RFR (S): 8230395: Code checks for NULL value returned from NEW_C_HEAP_ARRAY which can not happen

[David Holmes]

Bug: https://bugs.openjdk.java.net/browse/JDK-8230395
webrev: http://cr.openjdk.java.net/~dholmes/8230395/webrev/

First, thanks to Leo for going through and finding the places that 
needed to be fixed. I didn't go looking for others.

For the most part I have deleted the NULL checks. A few notes:

- changed to NEW_C_HEAP_ARRAY_RETURN_NULL in a couple of places where it 
was more consistent with the general recoverability approach of the code 
in question (and did the opposite change in one place)
- for the "perf" changes I also noticed that we were checking for NULL 
after doing "new SomeCHeapObj()" which also cannot return NULL, so 
removed those NULL checks too
- the JVMCI thread counter changes became a bit more extensive due to 
the fact a boolean method could now only every return true. So it was 
changed to void and that had to filter all the way back up to the JVMCI 
Java API. The JVMCI/Graal folk need to approve this

Testing: tier 1-3 sanity tests (in progress)

Thanks,
David